The present invention relates to a decoder, and more particularly, to processing related with the reproduction of data recorded in a predetermined format at a burst cutting area (“BCA”) of a disc medium of a decoder.
For example, a digital versatile disc (DVD) has a certain recording section, or BCA, as shown in FIG. 1. The BCA is formed by a striped pattern, which is defined by radially extending stripes, in correspondence with the data that is to be recorded. Identification information, which differs between each disc medium, or encoding and decoding keys may be recorded in the striped pattern. Illegal copying of the information recorded on a disc medium may be prevented by recording identification information or the like in the BCA.
FIG. 2 illustrates the format of the data recorded in the BCA. The data recorded in the BCA basically has one byte of a synchronization pattern (synch SB or synch RS) added to the head of every four bytes of data. One byte of a first synchronization pattern (synch SBBCA) and four bytes of preamble data (BCA preamble) are added to the head of the data recorded on the BCA.
The total five bytes of the first synchronization pattern and the preamble data are followed by data configured by a multiple of twenty bytes. In the following data, one byte of a second synchronization pattern (re-synch RS) is added to the head of every four bytes of the information data that is to be recorded. As shown in FIG. 2, different second synchronization patterns RSBCA1, RSBCA2, . . . are added to every sixteen bytes. As denoted by D0, D1, . . . in FIG. 2, four bytes of error detection data, or an error detection code (EDC), are added to the information data that is a multiple of sixteen bytes.
The EDC is followed by a parity configured by sixteen bytes, as denoted by C0,0, C1,0, . . . in FIG. 2. The parity is added to the information data and the EDC to function as error correction data, or an error correction code (ECC). One byte of a third synchronization pattern (re-synch RSBCA13) is added to the head of every four bytes of the parity. Every third synchronization pattern has the same value.
The parity data is followed by one byte of a fourth synchronization pattern (re-synch RSBCA13), four bytes of postamble data (BCA postamble), and one byte of a fifth synchronization pattern (re-synch RSBCA15).
Among the multiple pieces of data, fixed data patterns are set for the first and fifth synchronization patterns, the preamble data, and the postamble data.
A predetermined modulation is performed on the data of FIG. 2 to generate channel data, which is recorded on the BCA. Basically, the modulation is phase modulation (phase encoding). The phase modulation is performed by modulating “0” to “10” or “1” to “01” in order to convert one-bit data to two-bit data.
The first and fifth synchronization patterns are set in an exceptional manner, as shown in FIG. 3. More specifically, the former half of these synchronization patterns are preset by the same eight-bit fixed pattern, which serves as channel bits. Thus, the modulation of “0” to “10” or “1” to “01” is not performed on the eight-bit data in the former half of these synchronization patterns.
With regard to the synch code, or the four bits of data bits in the latter half of each synchronization pattern, different values are designated for each synchronization pattern. The synch codes undergo modulation in which “0” is converted to “10” and “1” is converted to “01”. For example, the synch code of the first synchronization pattern SBBCA having four bits of data bit, which is “0000”, undergoes phase modulation and is converted to eight bits of channel bits, which is “10101010”. In this manner, the eight bits of the fixed pattern and the phase-modulated eight bits of channel bits generate the channel data of each synchronization pattern. The channel data further undergoes return to zero (RZ) modulation before being recorded in the BCA.
In this manner, data is recorded to the BCA in the predetermined format. Thus, a decoder may be used to retrieve the identification information, encoding key, and decoding key that are included in each disc medium. The decoder decodes the data recorded in the BCA to perform error correction in accordance with the parities and retrieve accurate information from the information data.
However, the information may not be accurately retrieved from the information data when the data recorded in the BCA includes a missing part when noise is mixed in during reproduction of the data. For example, when the first synchronization pattern SBBCA cannot be detected, the head of the information data cannot be identified. Thus, decoding cannot be performed subsequently. Further, if the third synchronization pattern (re-synch RSBCA13)added to the head of every four bytes of the ECC parity cannot be detected, this may interfere with error correction or the identification of the end of the information data during data reproduction.